This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Mobile terminals require hand over functionality with communications services. For example, when a user moves and/or changes an access network interface, it is important that his or her call not be interrupted during the process. Some access networks implement mobility in layer 2 (e.g. wireless code division multiple access (WCDMA) and Global System for Mobile Communication (GSM)) or by using mobile IP (e.g. WiMAX or Internet-High-Speed Downlink Packet Access (I-HSDPA)). However, there are currently many types of IP networks that do not offer mobility by any mechanism, for example in the case of Wireless Local Area Network (WLAN) hotspots. Additionally, the use of Mobile IP requires the use of a home agent, and the home agent affects the traffic flows (e.g., traffic travels via the home agent).
Multi-radio terminals are becoming increasingly common as the technology surrounding these devices continues to improve at a substantial rate. As a result, a mobile terminal is now more likely than in the past to have many different radio interfaces that it can utilize for communications purposes. For example, a single mobile terminal may be capable of supporting GSM, WCDMA and WLAN. In future products, WiMAX and HSDPA are also expected to be incorporated, resulting in still more interfaces for a terminal.
Traditionally, hand over functionality has been integrated into the mobile networks. However, with several different technologies currently emerging, the hand over implementation is becoming more and more complex (e.g. hand over from GSM to WLAN). With IP networks becoming common, mobility is often being implemented by using mobile IP. There is also currently ongoing work to implement a voice call continuity service that focuses on the hand over from circuit switched voice system to packet voice systems.
Currently, a problem occurs whenever IP end points move and utilize the nomadic mobility provided by IP networks via, for example, the Dynamic Host Configuration Protocol (DHCP). When a terminal starts to use a new interface, or when the terminal moves, e.g. from one hotspot to another, it is common for the applications IP address and terminal routing table to change, as the IP address is tied to an interface. This causes current communications applications to loose connectivity. In IP-based networking, the applications are unaware of the access technologies that are used, and terminal applications usually only send packets to some destination IP address that the terminal routes according to the terminal's routing table (the routing table chooses the interface to be used).
In most instances, the routing table utilizes a default route that points to a connected interface that has the highest priority. It is possible that, during a communications session, the terminal may attach to a higher priority interface (e.g. WLAN) and the default route changes, causing an ongoing communications session to drop. It is also possible that the terminal may move out of coverage for a certain interface (e.g., out of a WLAN hot spot) so that the default route starts pointing to some other interface (e.g., WCDMA). Whenever the used interface changes, the IP address also changes. Otherwise, returning packets may experience black hole routing, as the previous interface may no longer be reachable from the Internet.